This invention relates to a disc clamping device for clamping a disc on a turntable of a disc cartridge player in which playback of the disc is accomplished by loading a cartridge housing the disc into the player.
Known in the art of a disc playback device is a device in which playback of a disc is accomplished by loading a cartridge housing the disc into the disc playback device.
As a disc cartridge and a disc cartridge player of this type, the inventor of the present invention and others have proposed in U.S. patent applications Nos. 721,666, 773,304, 781,768 and 781,751 a disc cartridge and a disc cartridge player capable of securely clamping the disc on the turntable even in a case where the disc to be played back is one with a relatively large thickness such as a Compact Disc for the Compact Disc Digital Audio System.
FIG. 8 shows a main part of this type of disc cartridge player. In FIG. 8, reference character A designates a disc cartridge and reference character B a disc playback device.
The disc cartridge A is formed in a box-like shape and includes an upper case 1 and a lower case 2 with a disc 3 being rotatably received between these cases 1 and 2. The upper case 1 is formed in its central portion with an opening 4. A disc stabilizer 5 is disposed in the opening 4 in such a manner that it is rotatable and also is prevented from disengaging from the opening 4 in the vertical direction. The lower case 2 is formed in its central portion with a turntable opening 6. A disc drive motor 8 is fixed to the lower surface of a chassis 7 of the disc playback device B. A disc-like turntable 10 is fixed to a shaft 9 of the motor 8. A clamper 12 having a steel ball 11 secured on its lower surface is disposed above the chassis 7. The clamper 12 is always urged downwardly by a spring 13 provided between the clamper 12 and the chassis 7 and also can be lifted compulsorily against the force of the spring 13 by unillustrated drive means.
In the player described above, the operation for loading the cartridge A into the disc playback device B is performed in the following manner. In a state in which the cartridge A is loaded, the clamper 12 is in a position in which it is elevated from the chassis 7 by a predetermined distance by the unillustrated drive means against the force of the spring 13. Then the cartridge A is displaced horizontally by a loading device (not shown) and introduced into a space defined between the turntable 10 and the clamper 12. Upon reaching of the turntable insertion opening 6 of the cartridge A to a position above the turntable 10, the cartridge A and the clamper 12 are lowered with a result that the turntable 10 enters the opening 6 and comes into abutting engagement with the lower surface of the disc 3. A projecting portion 10a of the turntable 10 enters the central opening of the disc 3 at this time thereby performing a horizontal positioning of the disc 3. In the meanwhile, the steel ball 11 of the clamper 12 located above the disc stabilizer 5 pushes the stabilizer 5 downwardly by the force of the spring 13 and the disc 3 thereby is held in position between the turntable 10 and the stabilizer 5. When the disc 3 has been held in position in the above described manner, the cartridge A and the clamper 12 cease their downward movement. By starting rotation of the motor 8 in this state, the turntable 10 rotates the disc 3 and the stabilizer 5 together with the stabilizer 5 being rotatably supported by the steel ball 11. In ejecting the disc cartridge A, the unillustrated drive means is operated to lift the cartridge A and the clamper 12 and then move the cartride A horizontally in the reverse direction thereby bringing it back to its original position.
In the disc cartridge player described above, the force to hold the disc 3, i.e., the force to hold the disc 3 between the turntable 10 and the stabilizer 5, is provided by the urging force of the spring 13 provided between the clamper 12 and the chassis 7 and, in ejecting the disc 3, the clamper 12 must be lifted by the clamper drive means against the force of this spring 13. Hence this player disadvantageously requires a spring of a very strong urging force for accurately holding the disc 3 and this in turn necessitates drive means of a very strong driving force for lifting the clamper 12 in ejecting the disc 3.
It is, therefore, an object of the present invention to provide a disc clamping device for a disc cartridge player which does not require a spring of such a strong force for urging the clamper but even is capable of obviating the clamper itself if desired while ensuring accurate holding of a disc on the turntable.